On a green hill, there is the Palacio de Buenavista, which is the Army's Headquarters: completed at the end of the 18th century, it is the oldest building in the square. It was the residence of the Dukes of Alba for about 20 years, but after the death of the famous Duchess who was a close friend of bullfighters and Goya's alleged mistress, it was inhabited by various prominent politicians or governors of the city, including General Juan Prim, who was assassinated in one of its rooms.